CSC311 – Chapter 1Fall 2020

Prof. Patrick Earl

Quick Recap

• What is the internet…• …made up of?

• …considered?

• What allows communication to take place?

Introduction

1.1 what is the Internet?

1.2 network edge• end systems, access networks, links

1.3 network core• packet switching, circuit switching, network structure

1.4 delay, loss, throughput in networks

1.5 protocol layers, service models

1.6 networks under attack: security

1.7 history

1-3

Introduction

A closer look at network structure:

▪ network edge:• hosts: clients and servers• servers often in data centers

▪ access networks, physical media: wired, wireless communication links

▪ network core: • interconnected routers

• network of networks

1-4

mobile network

global ISP

regional ISP

home network

institutionalnetwork

Introduction

Access networks and physical media

Q: How to connect end systems to edge router?

▪ residential access nets

▪ institutional access networks (school, company)

▪ mobile access networks

keep in mind:

▪ bandwidth (bits per second) of access network?

▪ shared or dedicated?

1-5

ISP

Introduction

Access network: digital subscriber line (DSL)

central office telephonenetwork

DSLAM

voice, data transmittedat different frequencies over

dedicated line to central office

▪ use existing telephone line to central office DSLAM

• data over DSL phone line goes to Internet

• voice over DSL phone line goes to telephone net

▪ < 2.5 Mbps upstream transmission rate (typically < 1 Mbps)

▪ < 24 Mbps downstream transmission rate (typically < 10 Mbps)

DSLmodem

splitter

DSL access multiplexer

1-6

Introduction

Access network: cable network

cablemodem

splitter

…

cable headend

Channels

V

I

D

E

O

V

I

D

E

O

V

I

D

E

O

V

I

D

E

O

V

I

D

E

O

V

I

D

E

O

D

A

T

A

D

A

T

A

C

O

N

T

R

O

L

1 2 3 4 5 6 7 8 9

frequency division multiplexing: different channels transmittedin different frequency bands

1-7

ISP

Introduction

data, TV transmitted at different frequencies over shared cable

distribution network

cablemodem

splitter

…

cable headend

CMTScable modem

termination system

▪ HFC: hybrid fiber coax

• asymmetric: up to 30Mbps downstream transmission rate, 2 Mbps upstream transmission rate

▪ network of cable, fiber attaches homes to ISP router

• homes share access network to cable headend

• unlike DSL, which has dedicated access to central office

Access network: cable network

1-8

Introduction

Access network: home network

to/from headend or central office

cable or DSL modem

router, firewall, NAT

wired Ethernet (1 Gbps)

wireless access point (54 Mbps)

wireless

devices

often combined in single box

1-9

Introduction

Enterprise access networks (Ethernet)

▪ typically used in companies, universities, etc.

▪ 10 Mbps, 100Mbps, 1Gbps, 10Gbps transmission rates

▪ today, end systems typically connect into Ethernet switch

Ethernet switch

institutional mail,web servers

institutional router

institutional link to ISP (Internet)

1-10

Introduction

Wireless access networks

• shared wireless access network connects end system to router• via base station aka “access point”

wireless LANs:▪ within building (100 ft.)

▪ 802.11b/g/n (WiFi): 11, 54, 450 Mbps transmission rate

wide-area wireless access▪ provided by telco (cellular)

operator, 10’s km

▪ between 1 and 10 Mbps

▪ 3G, 4G: LTE

to Internet

to Internet

1-11

Host: sends packets of data

host sending function:

▪ takes application message

▪ breaks into smaller chunks, known as packets, of length Lbits

▪ transmits packet into access network at transmission rate R• link transmission rate,

aka link capacity, aka link bandwidth

R: link transmission ratehost

12

two packets,

L bits each

packettransmission

delay

time needed totransmit L-bit

packet into link

L (bits)

R (bits/sec)= =

1-12Introduction

Introduction

Physical media

• bit: propagates betweentransmitter/receiver pairs

• physical link: what lies between transmitter & receiver

• guided media:

• signals propagate in solid media: copper, fiber, coax

• unguided media:

• signals propagate freely, e.g., radio

twisted pair (TP)

▪ two insulated copper wires• Category 5: 100 Mbps, 1

Gbps Ethernet

• Category 6: 10Gbps

1-13

Introduction

Physical media: coax, fiber

coaxial cable:

▪ two concentric copper conductors

▪ bidirectional

▪ broadband:• multiple channels on cable

• HFC

fiber optic cable:▪ glass fiber carrying light

pulses, each pulse a bit

▪ high-speed operation:• high-speed point-to-point

transmission (e.g., 10’s-100’s Gbps transmission rate)

▪ low error rate: • repeaters spaced far apart

• immune to electromagnetic noise

1-14

Introduction

Physical media: radio

• signal carried in electromagnetic spectrum

• no physical “wire”

• bidirectional

• propagation environment effects:

• reflection

• obstruction by objects

• interference

radio link types:▪ terrestrial microwave

• e.g. up to 45 Mbps channels

▪ LAN (e.g., WiFi)

• 54 Mbps

▪ wide-area (e.g., cellular)

• 4G cellular: ~ 10 Mbps

▪ satellite

• Kbps to 45Mbps channel (or multiple smaller channels)

• 270 msec end-end delay

• geosynchronous versus low altitude

1-15

Introduction

Chapter 1: roadmap

1.1 what is the Internet?

1.2 network edge• end systems, access networks, links

1.3 network core• packet switching, circuit switching, network structure

1.4 delay, loss, throughput in networks

1.5 protocol layers, service models

1.6 networks under attack: security

1.7 history

1-16

Introduction

• mesh of interconnected routers

• packet-switching: hosts break application-layer messages into packets• forward packets from one

router to the next, across links on path from source to destination

• each packet transmitted at full link capacity

The network core

1-17

Introduction

Packet-switching: store-and-forward

• takes L/R seconds to transmit (push out) L-bit packet into link at R bps

• store and forward: entire packet must arrive at router before it can be transmitted on next link

one-hop numerical example:

▪ L = 7.5 Mbits

▪ R = 1.5 Mbps

▪ one-hop transmission delay = 5 sec

more on delay shortly …

1-18

sourceR bps

destination123

L bitsper packet

R bps

▪ end-end delay = 2L/R (assuming zero propagation delay)

Introduction

Packet Switching: queueing delay, loss

A

B

CR = 100 Mb/s

R = 1.5 Mb/sD

Equeue of packetswaiting for output link

1-19

queuing and loss: ▪ if arrival rate (in bits) to link exceeds transmission rate of link for a period of time:

• packets will queue, wait to be transmitted on link

• packets can be dropped (lost) if memory (buffer) fills up

Two key network-core functions

forwarding: move packets from router’s input to appropriate router output

Introduction 1-20

routing: determines source-destination route taken by packets

▪ routing algorithms

routing algorithm

local forwarding table

header value output link

0100

0101

0111

1001

3

2

2

1

1

23

destination address in arriving

packet’s header

Introduction

Alternative core: circuit switching

end-end resources allocated to, reserved for “call” between source & dest:

• in diagram, each link has four circuits. • call gets 2nd circuit in top link

and 1st circuit in right link.

• dedicated resources: no sharing• circuit-like (guaranteed)

performance

• circuit segment idle if not used by call (no sharing)

• commonly used in traditional telephone networks

1-21

Introduction

Circuit switching: FDM versus TDM

FDM

frequency

timeTDM

frequency

time

4 users

Example:

1-22

Introduction

Packet switching versus circuit switching

example:

• 1 Mb/s link

• each user: • 100 kb/s when “active”

• active 10% of time

• circuit-switching:• 10 users

• packet switching:• with 35 users, probability >

10 active at same time is less than .0004 *

packet switching allows more users to use network!

Nusers

1 Mbps link

Q: how did we get value 0.0004?

Q: what happens if > 35 users ?

1-23

* Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/interactive/

Introduction

• great for bursty data

• resource sharing

• simpler, no call setup

• excessive congestion possible: packet delay and loss

• protocols needed for reliable data transfer, congestion control

• Q: How to provide circuit-like behavior?

• bandwidth guarantees needed for audio/video apps

• still an unsolved problem (chapter 7)

is packet switching a “slam dunk winner?”

Q: human analogies of reserved resources (circuit switching)

versus on-demand allocation (packet-switching)?

Packet switching versus circuit switching

1-24

Internet structure: network of networks

▪ End systems connect to Internet via access ISPs (Internet Service Providers)

• residential, company and university ISPs

▪ Access ISPs in turn must be interconnected.

• so that any two hosts can send packets to each other

▪ Resulting network of networks is very complex

• evolution was driven by economics and national policies

▪ Let’s take a stepwise approach to describe current Internet structure

Introduction 1-25

Internet structure: network of networks

Question: given millions of access ISPs, how to connect them together?

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnetaccess

net

accessnet

Introduction 1-26

Internet structure: network of networks

Option: connect each access ISP to every other access ISP?

accessnet

accessnet

connecting each access ISP

to each other directly doesn’t

scale: O(N2) connections.

Introduction 1-27

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnetaccess

net

accessnet

Internet structure: network of networks

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnetaccess

net

accessnet

Option: connect each access ISP to one global transit ISP?

Customer and provider ISPs have economic agreement.

Introduction 1-28

global

ISP

ISP C

ISP B

ISP A

Internet structure: network of networks

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnetaccess

net

accessnet

But if one global ISP is viable business, there will be competitors ….

Introduction 1-29

accessnet

ISP C

ISP B

ISP A

Internet structure: network of networks

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnetaccess

net

accessnet

Introduction 1-30

accessnet

But if one global ISP is viable business, there will be competitors …. which must be interconnected

IXP

peering link

Internet exchange point

IXP

ISP C

ISP B

ISP A

Internet structure: network of networks

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnet

accessnetaccess

net

accessnet

Introduction 1-31

accessnet

IXP

IXPaccessnet

accessnet

accessnet

regional net

… and regional networks may arise to connect access nets to ISPs

Introduction

Internet structure: network of networks

• at center: small # of well-connected large networks• “tier-1” commercial ISPs (e.g., Level 3, Sprint, AT&T, NTT), national &

international coverage

• content provider network (e.g., Google): private network that connects it data centers to Internet, often bypassing tier-1, regional ISPs 1-32

IXP IXP IXP

Tier 1 ISP Tier 1 ISP Google

Regional ISP Regional ISP

access

ISP

access

ISP

access

ISP

access

ISP

access

ISP

access

ISP

access

ISP

access

ISP

Introduction

Tier-1 ISP: e.g., Sprint

1-33

…

to/from customers

peering

to/from backbone

…

………

POP: point-of-presence

Introduction

Chapter 1: roadmap1.1 what is the Internet?

1.2 network edge• end systems, access networks, links

1.3 network core• packet switching, circuit switching, network structure

1.4 delay, loss, throughput in networks

1.5 protocol layers, service models

1.6 networks under attack: security

1.7 history

1-34

A

B

Introduction

How do loss and delay occur?

packets queue in router buffers

▪ packet arrival rate to link (temporarily) exceeds output link capacity

▪ packets queue, wait for turnpacket being transmitted (delay)

packets queueing (delay)

free (available) buffers: arriving packets

dropped (loss) if no free buffers

1-35

Introduction

Four sources of packet delay

dproc: nodal processing▪ check bit errors

▪ determine output link

▪ typically < msec

dqueue: queueing delay▪ time waiting at output link for

transmission

▪ depends on congestion level of router

1-36

propagation

nodal

processing queueing

dnodal = dproc + dqueue + dtrans + dprop

A

B

transmission

Introduction

dtrans: transmission delay:

▪ L: packet length (bits)

▪ R: link bandwidth (bps)

▪ dtrans = L/R

dprop: propagation delay:

▪ d: length of physical link

▪ s: propagation speed (~2x108 m/sec)

▪ dprop = d/s

Four sources of packet delay

1-37* Check out the Java applet for an interactive animation on trans vs. prop delay

dtrans and dprop

very different

* Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/interactive/

propagation

nodal

processing queueing

dnodal = dproc + dqueue + dtrans + dprop

A

B

transmission

Introduction

Caravan analogy

• cars “propagate” at 100 km/hr

• toll booth takes 12 sec to service car (bit transmission time)

• car ~ bit; caravan ~ packet

• Q: How long until caravan is lined up before 2nd toll booth?

• time to “push” entire caravan through toll booth onto highway = 12*10 = 120 sec

• time for last car to propagate from 1st to 2nd toll both: 100km/(100km/hr)= 1 hr

• A: 62 minutes

toll

booth

toll

booth

ten-car

caravan

100 km 100 km

1-38

Introduction

Caravan analogy (more)

• suppose cars now “propagate” at 1000 km/hr

• and suppose toll booth now takes one min to service a car

• Q: Will cars arrive to 2nd booth before all cars serviced at first booth?

• A: Yes! after 7 min, first car arrives at second booth; three cars still at first booth

toll

booth

toll

booth

ten-car

caravan

100 km 100 km

1-39

Introduction

• R: link bandwidth (bps)

• L: packet length (bits)

• a: average packet arrival rate

traffic intensity = La/R

▪ La/R ~ 0: avg. queueing delay small

▪ La/R -> 1: avg. queueing delay large

▪ La/R > 1: more “work” arriving

than can be serviced, average delay infinite!

ave

rag

e q

ue

ue

ing

d

ela

y

La/R ~ 0

La/R -> 11-40* Check online interactive animation on queuing and loss

Queueing delay (revisited)

Introduction

“Real” Internet delays and routes

• what do “real” Internet delay & loss look like?

• traceroute program: provides delay measurement from source to router along end-end Internet path towards destination. For all i:• sends three packets that will reach router i on path

towards destination• router i will return packets to sender• sender times interval between transmission and reply.

3 probes

3 probes

3 probes

1-41

Introduction

“Real” Internet delays, routes

1 cs-gw (128.119.240.254) 1 ms 1 ms 2 ms2 border1-rt-fa5-1-0.gw.umass.edu (128.119.3.145) 1 ms 1 ms 2 ms3 cht-vbns.gw.umass.edu (128.119.3.130) 6 ms 5 ms 5 ms4 jn1-at1-0-0-19.wor.vbns.net (204.147.132.129) 16 ms 11 ms 13 ms 5 jn1-so7-0-0-0.wae.vbns.net (204.147.136.136) 21 ms 18 ms 18 ms 6 abilene-vbns.abilene.ucaid.edu (198.32.11.9) 22 ms 18 ms 22 ms7 nycm-wash.abilene.ucaid.edu (198.32.8.46) 22 ms 22 ms 22 ms8 62.40.103.253 (62.40.103.253) 104 ms 109 ms 106 ms9 de2-1.de1.de.geant.net (62.40.96.129) 109 ms 102 ms 104 ms10 de.fr1.fr.geant.net (62.40.96.50) 113 ms 121 ms 114 ms11 renater-gw.fr1.fr.geant.net (62.40.103.54) 112 ms 114 ms 112 ms12 nio-n2.cssi.renater.fr (193.51.206.13) 111 ms 114 ms 116 ms13 nice.cssi.renater.fr (195.220.98.102) 123 ms 125 ms 124 ms14 r3t2-nice.cssi.renater.fr (195.220.98.110) 126 ms 126 ms 124 ms15 eurecom-valbonne.r3t2.ft.net (193.48.50.54) 135 ms 128 ms 133 ms16 194.214.211.25 (194.214.211.25) 126 ms 128 ms 126 ms17 * * *18 * * *

19 fantasia.eurecom.fr (193.55.113.142) 132 ms 128 ms 136 ms

traceroute: gaia.cs.umass.edu to www.eurecom.fr

3 delay measurements from

gaia.cs.umass.edu to cs-gw.cs.umass.edu

* means no response (probe lost, router not replying)

trans-oceanic

link

1-42* Do some traceroutes from exotic countries at www.traceroute.org

Introduction

Packet loss• queue (aka buffer) preceding link in buffer has finite

capacity

• packet arriving to full queue dropped (aka lost)

• lost packet may be retransmitted by previous node, by source end system, or not at all

A

B

packet being transmitted

packet arriving to

full buffer is lost

buffer

(waiting area)

1-43* Check out the Java applet for an interactive animation on queuing and loss

Introduction

Throughput

• throughput: rate (bits/time unit) at which bits transferred between sender/receiver• instantaneous: rate at given point in time

• average: rate over longer period of time

server, withfile of F bits

to send to client

link capacityRs bits/sec

link capacityRc bits/sec

server sends bits (fluid) into pipe

pipe that can carryfluid at rateRs bits/sec)

pipe that can carryfluid at rateRc bits/sec)

1-44

Introduction

Throughput (more)

• Rs < Rc What is average end-end throughput?

Rs bits/sec Rc bits/sec

▪ Rs > Rc What is average end-end throughput?

link on end-end path that constrains end-end throughput

bottleneck link

Rs bits/sec Rc bits/sec

1-45

Introduction

Throughput: Internet scenario

10 connections (fairly) share

backbone bottleneck link R bits/sec

Rs

Rs

Rs

Rc

Rc

Rc

R

• per-connection end-end throughput: min(Rc,Rs,R/10)

• in practice: Rc or Rs is often bottleneck

1-46* Check out the online interactive exercises for more

examples: http://gaia.cs.umass.edu/kurose_ross/interactive/

Introduction

Chapter 1: roadmap1.1 what is the Internet?

1.2 network edge• end systems, access networks, links

1.3 network core• packet switching, circuit switching, network structure

1.4 delay, loss, throughput in networks

1.5 protocol layers, service models

1.6 networks under attack: security

1.7 history

1-47

Introduction

Protocol “layers”

Networks are complex,

with many “pieces”:▪ hosts

▪ routers

▪ links of various media

▪ applications

▪ protocols

▪ hardware, software

Question:is there any hope of

organizing structure of network?

…. or at least our discussion of networks?

1-48

Introduction

Organization of air travel

• a series of steps

ticket (purchase)

baggage (check)

gates (load)

runway takeoff

airplane routing

ticket (complain)

baggage (claim)

gates (unload)

runway landing

airplane routing

airplane routing

1-49

Introduction

ticket (purchase)

baggage (check)

gates (load)

runway (takeoff)

airplane routing

departure

airportarrival

airport

intermediate air-traffic

control centers

airplane routing airplane routing

ticket (complain)

baggage (claim

gates (unload)

runway (land)

airplane routing

ticket

baggage

gate

takeoff/landing

airplane routing

Layering of airline functionality

layers: each layer implements a service

▪ via its own internal-layer actions

▪ relying on services provided by layer below

1-50

Introduction

Why layering?dealing with complex systems:• explicit structure allows identification, relationship

of complex system’s pieces• layered reference model for discussion

• modularization eases maintenance, updating of system• change of implementation of layer’s service

transparent to rest of system• e.g., change in gate procedure doesn’t affect rest of

system

• layering considered harmful?

1-51

Introduction

Internet protocol stack

• application: supporting network applications• FTP, SMTP, HTTP

• transport: process-process data transfer• TCP, UDP

• network: routing of datagrams from source to destination• IP, routing protocols

• link: data transfer between neighboring network elements• Ethernet, 802.111 (WiFi), PPP

• physical: bits “on the wire”

application

transport

network

link

physical

1-52

Introduction

ISO/OSI reference model

• presentation: allow applications to interpret meaning of data, e.g., encryption, compression, machine-specific conventions

• session: synchronization, checkpointing, recovery of data exchange

• Internet stack “missing” these layers!• these services, if needed, must be

implemented in application• needed?

application

presentation

session

transport

network

link

physical

1-53

Introduction

source

application

transport

network

link

physical

HtHn M

segment Ht

datagram

destination

application

transport

network

link

physical

HtHnHl M

HtHn M

Ht M

M

network

link

physical

link

physical

HtHnHl M

HtHn M

HtHn M

HtHnHl M

router

switch

Encapsulationmessage M

Ht M

Hn

frame

1-54

Introduction

Chapter 1: roadmap1.1 what is the Internet?

1.2 network edge• end systems, access networks, links

1.3 network core• packet switching, circuit switching, network structure

1.4 delay, loss, throughput in networks

1.5 protocol layers, service models

1.6 networks under attack: security

1.7 history

1-55

Introduction

Network security

• field of network security:• how bad guys can attack computer networks

• how we can defend networks against attacks

• how to design architectures that are immune to attacks

• Internet not originally designed with (much) security in mind• original vision: “a group of mutually trusting users

attached to a transparent network”☺

• Internet protocol designers playing “catch-up”

• security considerations in all layers!

1-56

Introduction

Bad guys: put malware into hosts via Internet

• malware can get in host from:

• virus: self-replicating infection by receiving/executing object (e.g., e-mail attachment)

• worm: self-replicating infection by passively receiving object that gets itself executed

• spyware malware can record keystrokes, web sites visited, upload info to collection site

• infected host can be enrolled in botnet, used for spam. DDoS attacks

1-57

Introduction

target

Denial of Service (DoS): attackers make resources (server, bandwidth) unavailable to legitimate traffic by overwhelming resource with bogus traffic

1. select target

2. break into hosts around

the network (see botnet)

3. send packets to target from

compromised hosts

Bad guys: attack server, network infrastructure

1-58

Introduction

Bad guys can sniff packets

packet “sniffing”:▪ broadcast media (shared Ethernet, wireless)▪ promiscuous network interface reads/records all packets (e.g.,

including passwords!) passing by

A

B

C

src:B dest:A payload

▪ wireshark software used for end-of-chapter labs is a (free) packet-sniffer

1-59

Introduction

Bad guys can use fake addresses

IP spoofing: send packet with false source address

A

B

C

src:B dest:A payload

1-60

… lots more on security (throughout, Chapter 8)

WannaCry Ransomware

• https://en.wikipedia.org/wiki/WannaCry_ransomware_attack

Introduction

Chapter 1: roadmap1.1 what is the Internet?

1.2 network edge• end systems, access networks, links

1.3 network core• packet switching, circuit switching, network structure

1.4 delay, loss, throughput in networks

1.5 protocol layers, service models

1.6 networks under attack: security

1.7 history

1-62

Introduction

Internet history

▪ 1961: Kleinrock -queueing theory shows effectiveness of packet-switching

▪ 1964: Baran - packet-switching in military nets

▪ 1967: ARPAnet conceived by Advanced Research Projects Agency

▪ 1969: first ARPAnet node operational

• 1972:

• ARPAnet public demo

• NCP (Network Control Protocol) first host-host protocol

• first e-mail program

• ARPAnet has 15 nodes

1961-1972: Early packet-switching principles

1-63

Introduction

• 1970: ALOHAnet satellite network in Hawaii

• 1974: Cerf and Kahn -architecture for interconnecting networks

• 1976: Ethernet at Xerox PARC

• late70’s: proprietary architectures: DECnet, SNA, XNA

• late 70’s: switching fixed length packets (ATM precursor)

• 1979: ARPAnet has 200 nodes

Cerf and Kahn’s internetworking principles:• minimalism, autonomy - no

internal changes required to interconnect networks

• best effort service model

• stateless routers

• decentralized control

define today’s Internet architecture

1972-1980: Internetworking, new and proprietary nets

Internet history

1-64

Introduction

• 1983: deployment of TCP/IP

• 1982: smtp e-mail protocol defined

• 1983: DNS defined for name-to-IP-address translation

• 1985: ftp protocol defined

• 1988: TCP congestion control

▪ new national networks: CSnet, BITnet, NSFnet, Minitel

▪ 100,000 hosts connected to confederation of networks

1980-1990: new protocols, a proliferation of networks

Internet history

1-65

Introduction

• early 1990’s: ARPAnet decommissioned

• 1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995)

• early 1990s: Web• hypertext [Bush 1945, Nelson

1960’s]• HTML, HTTP: Berners-Lee• 1994: Mosaic, later Netscape• late 1990’s:

commercialization of the Web

late 1990’s – 2000’s:

• more killer apps: instant messaging, P2P file sharing

• network security to forefront

• est. 50 million host, 100 million+ users

• backbone links running at Gbps

1990, 2000’s: commercialization, the Web, new apps

Internet history

1-66

Introduction

2005-present• ~5B devices attached to Internet (2016)

• smartphones and tablets

• aggressive deployment of broadband access

• increasing ubiquity of high-speed wireless access

• emergence of online social networks: • Facebook: ~ one billion users

• service providers (Google, Microsoft) create their own networks• bypass Internet, providing “instantaneous” access to

search, video content, email, etc.

• e-commerce, universities, enterprises running their services in “cloud” (e.g., Amazon EC2)

Internet history

1-67

Introduction

Introduction: summary

covered a “ton” of material!• Internet overview

• what’s a protocol?

• network edge, core, access network• packet-switching versus

circuit-switching• Internet structure

• performance: loss, delay, throughput

• layering, service models

• security

• history

you now have:

• context, overview, “feel”of networking

• more depth, detail to follow!

1-68

Introduction 1-69

Chapter 1Additional Slides

Transport (TCP/UDP)

Network (IP)

Link (Ethernet)

Physical

application

(www browser,

email client)

application

OS

packet

capture

(pcap)

packet

analyzer

copy of all

Ethernet

frames

sent/receive

d